Type Alias StabilityComputed

pub type StabilityComputed = Stability<AllowToggleComputed>;

Stability where allow_toggle has already been computed.

Aliased Type

enum StabilityComputed {
    Stable {
        allow_toggle: AllowToggleComputed,
    },
    Unstable {
        nightly_feature: Symbol,
        allow_toggle: AllowToggleComputed,
    },
    Forbidden {
        reason: &'static str,
    },
}

Variants

Stable

This target feature is stable, it can be used in #[target_feature] and #[cfg(target_feature)].

Fields

allow_toggle: AllowToggleComputed

When enabling/disabling the feature via -Ctarget-feature or #[target_feature], determine if that is allowed.

Unstable

This target feature is unstable. It is only present in #[cfg(target_feature)] on nightly and using it in #[target_feature] requires enabling the given nightly feature.

Fields

nightly_feature: Symbol

This must be a language feature, or else rustc will ICE when reporting a missing feature gate!

allow_toggle: AllowToggleComputed

See Stable::allow_toggle comment above.

Forbidden

This feature can not be set via -Ctarget-feature or #[target_feature], it can only be set in the target spec. It is never set in cfg(target_feature). Used in particular for features that change the floating-point ABI.

Fields

reason: &'static str

Implementations

impl StabilityComputed

pub fn toggle_allowed(&self, enable: bool) -> Result<(), &'static str>

Returns whether the feature may be toggled via #[target_feature] or -Ctarget-feature. (It might still be nightly-only even if this returns true, so make sure to also check requires_nightly.)

impl<Toggleability> Stability<Toggleability>

pub fn in_cfg(&self) -> bool

Returns whether the feature can be used in cfg(target_feature) ever. (It might still be nightly-only even if this returns true, so make sure to also check requires_nightly.)

pub fn requires_nightly(&self) -> Option<Symbol>

Returns the nightly feature that is required to toggle this target feature via #[target_feature]/-Ctarget-feature or to test it via cfg(target_feature). (For cfg we only care whether the feature is nightly or not, we don’t require the feature gate to actually be enabled when using a nightly compiler.)

Before calling this, ensure the feature is even permitted for this use:

• for #[target_feature]/-Ctarget-feature, check allow_toggle()
• for cfg(target_feature), check in_cfg

Layout

Note: Most layout information is completely unstable and may even differ between compilations. The only exception is types with certain repr(...) attributes. Please see the Rust Reference's “Type Layout” chapter for details on type layout guarantees.

Size: 40 bytes

Size for each variant:

• Stable: 36 bytes
• Unstable: 36 bytes
• Forbidden: 20 bytes

Trait Implementations

impl<Toggleability: Clone> Clone for Stability<Toggleability>

fn clone(&self) -> Stability<Toggleability>

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<Toggleability: Debug> Debug for Stability<Toggleability>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<CTX, Toggleability: HashStable<CTX>> HashStable<CTX> for Stability<Toggleability>

fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher)